A hinge assembly includes a pivot shaft, a rotary member and a steady member sleeved on the pivot shaft. The rotary member and the steady member faces each other and are rotatable relative to each other. The rotary member forms a first peak, and the steady member forms a second peak. A friction portion is formed between the rotary member and the steady member. A thickness of the friction portion exceeds or equals to a thickness of either of the first peak or the second peak, and is less than the combined thickness of the first peak and the second peak. A support mechanism using the hinge assembly is also provided.